2548-1479) 272 concept for a lng gas handling system for a

International Journal of Marine Engineering Innovation and Research, Vol. 1(4), Sept. 2017. 272-283

(pISSN: 2541-5972, eISSN: 2548-1479) 272

Concept for a LNG Gas Handling System for a

Dual Fuel Engine

Michael Rachow1, Steffen Loest

2, Leonardo Risman Maruli Sitinjak

3

Abstractnowadays, ships are using LNG as main engine fuel because based on the facts that LNG has no sulphur

content, and its combustion process, LNG produces low NOx content compared to heavy fuel oil and marine diesel oil. LNG

is not only produces low gas emission, but may have economic advantages. In the engine laboratory of maritime studies

department in Warnemunde, Germany, there is a diesel engine type MAN 6L23/30 A, where the mode operation of these

engine would be changed to dual fuel engine mode operation. Therefore, in this research, the use dual fuel engine will be

compared where it will utilize natural gas and marine diesel oil and select the required components for fuel gas supply

system. By conducting the process calculation, engine MAN 6L23/30 A requires the capacity natural gas of 12.908 for 5

days at full load. A concept for LNG supply system would be arranged from storage tank until engine manifold.

Germanischer Lloyd and Project Guide of dual fuel engine will be used as a guidelines to develop an optimal design and

arrangement which comply with the regulation.

Keywordsliquefied natural gas (LNG), dual fuel engine, fuel gas consumption analysis, concept of LNG supply system.

I. INTRODUCTION1

Liquefied natural gas (LNG) has been used as

marine fuel for more than 50 years since the world’s first

commercial seaborne trade of LNG began in 1964,

shipping LNG from Algeria to the U.K [1]. The liquefied

natural gas as a marine fuel is regarded as a proven

solution for marine applications. The number of ships

using LNG as fuel is increasing fast and more and more

infrastructure projects are planned or proposed along the

main shipping lanes. 63 LNG-fuelled ships (excluding

LNG carriers) already operate worldwide, while another

76 new buildings are confirmed (as of May 2015) [2].

The main emission product from a diesel engine are

, , and particulate matter (PM). These

emissions can increasing the temperature on earth, affect

the air quality, global warming and other health

problems that can impact the environmental. The use of

LNG as marine fuel is the proven solution and will

contribute to a reduction of these emissions. These

reductions will have significant environmental

benefits such as improved local air quality, reduced

acid rain and contribute to limit global warming [3-19].

According to DNV GL, when LNG is used as a ship

fuel and in the replacement of conventional oil-based

fuels (heavy fuel oil, marine gas oil, or distillate fuels) is

the significant reduction in local air pollution - ranging

from emissions of and to carbon dioxide,

particulates (PM) and black carbon. The complete

removal of and particle PM emissions and a

reduction of emission of up to 85% by using LNG is

a strong argument for the use of LNG, especially in

Michael Rachow, Department of Maritime Studies, Hochschule

Wismar, Wismar, 23966, Germany. E-mail: michael.rachow@hs-

wismar.de

Steffen Loest, Department of Maritime Studies, Hochschule Wismar, Wismar, 23966, Germany. E-mail: [email protected]

Leonardo Risman Maruli Sitinjak, Department of Marine

Engineering, Institut Teknologi Sepuluh Nopember, Campus ITS Sukolilo-Surabaya, 60111, Indonesia. E-mail: [email protected]

coastal and sensitive ecosystems. In addition, LNG also

reduces emissions by at least 20%. As a fuelling

option, LNG offers multiple advantages to both human

health and the environment.

One of the main reason that makes LNG become the

preferable fuel is the lower price compared to Heavy

Fuel Oil (HFO), Marine Diesel Oil (MDO) and Low

Sulphur Heavy Fuel Oil (LSHFO). DNV GL was made

fuel price scenario for the basic assumption. Starting

year for the fuel price scenario is 2010 and 650 $/t

(=15.3 $/mmBTU) for HFO and 900 $/t (=21.2

$/mmBTU) for MGO are set. LNG is set at 13

$/mmBTU which includes small-scale distribution costs

of 4 $/mmBTU [3-11].

II. METHOD

A. Problem of Statement

In this research, the main problem is changing the engine

operation mode from diesel to dual fuel which installed

inside the engine laboratory, at the department of

maritime studies in Warnemünde. The diesel engine type

is MAN 6L23/30A. According to the problem above, it

generated problem formulation, such as gas consumption

at variation loads, components of the gas supply system,

design P & I concept including special requirements and

safety aspects.

B. Literature Study

Literature study is the stage to get all the information to

solve the problem obtained. Many information should be

obtained, such as basic theory of LNG characteristics,

how to calculate the fuel oil and fuel gas consumption,

what are the supporting components of fuel gas supply

system, what is the consideration to design the concept

of fuel gas supply system, how to install the required

component into the laboratory building and many others.

Most of the information regarding concept design of fuel

gas supply system can be obtained from Germanischer

Lloyd as classification society and dual fuel engine

project guide. Some information are also can be obtained

from papers, journals, research and researches that able

to support this research.


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C. Collecting Data

In this stage, data collection is required to develop the

concept of fuel gas supply system. The data supported in

this research are engine specifications, dual fuel engine

project guide, and classification regulation of gas supply

systems. Engine project guide is required to find out the

engine specifications and engine dimensions. In this

research, the calculation of fuel oil consumption and

vaporizer is based on data actual of engine operation.

Therefore, the engine will be operated to get the actual

data of specific fuel oil consumption (SFOC), engine

water cooling temperature and exhaust gas temperature.

D. Fuel Oil Consumption Calculation

In this stage, fuel oil consumption will be calculated in

several variations of load, such as 10%, 25%, 50%, 75%,

and 100%. The fuel oil consumption will be calculated

based on the data from project guide and data actual of

engine operation. Therefore, SFOC from project guide

6L23/30 A MAN is required to calculate the fuel

consumption. The data actual of SFOC will be obtained

after the engine operated.

E. Fuel Gas Consumption Calculation

In this stage, fuel gas consumption will be calculated to

find out the storage tank capacity to store the fuel for

certain time of operation, fuel pump capacity, vaporizing

system and gas valve unit specification. The value of

specific fuel gas consumption (SFGC) is required to

calculate the fuel gas consumption. There is no

information about SFGC for engine MAN 6L23/30 A.

Therefore, the dual fuel engine project guide is needed as

reference to get the value of SFGC, such as MAN 51/60

DF, MAN 35/44 DF and Wartsila 34 DF. These engine

was converted from single fuel to dual fuel engine. The

value of SFGC from each dual fuel engine project guide

will be compared and choose the correct one as reference

to calculate the fuel gas consumption of engine MAN

6L23/30 A.

F. Determine the Required Components of Fuel Gas

Supply System

This stage is aims to analyse the components required for

gas supply system and the decision of components is

based on the classification society and dual fuel engine

project guide. Germanischer Lloyd regulation will be

used as the classification society. The essential

components is required to support the fuel gas supply

system, such as LNG tank, water spray pump, LNG

pump, vaporizer, and gas valve unit (GVU). All the

specification of these components will be obtained based

on the fuel gas consumption result. The output of this

stage is to determine the required components that meet

to the engine requirement, dual fuel engine project guide,

and classification societies.

G. Design the Concept of Fuel Gas Supply System

After every consideration is met the requirement, then

the next step is design the fuel gas supply system. In this

stage, to design a P&I concept including special

requirements for LNG and safety aspects from store tank

until engine manifold. Safety aspects will be arranged

according to Germanischer Lloyd regulation, component

manufacturer requirement, and dual fuel engine project

guide.

H. Installation Suggest for the Plant

After the concept design of fuel gas supply system met to

the regulation and project guide of dual fuel engine, then

all the components can be installed to the laboratory. In

this stage, the placement location of each component will

be considered because the laboratory at the department

of maritime studies in Warnemünde has limited space.

The consideration of installation suggest for the

components of fuel gas supply system in the laboratory

building should be based on the classification societies.

I. Conclusion

The conclusion of this research is to obtain the optimum

concept design of gas supply system and safety aspects

from storage tank until engine manifold that based on

Germanischer Lloyd regulation and dual fuel engine

project guide.

III. RESULTS AND DISCUSSION

A. Engine Overview

This research use engine type MAN 6l23/30 A as case

study. The engine is installed inside the engine

laboratory, at the department of maritime studies in

Warnemünde. This engine had a power of 960 kW and

use marine diesel oil (MDO) as the main fuel. This

engine is equipped with water brake system. A water

brake system is a type of fluid coupling used to absorb

mechanical energy and usually consists of a turbine or

propeller mounted in an enclosure filled with water. The

water brake is utilized to measure the power output of

the engine. The basic operation of a water brake uses the

principle of viscous coupling. The output shaft of the

engine is coupled to a fan that spins inside a concentric

housing. While the engine is running, the housing is

filled with a controlled amount of water. The more water

that is allowed into the housing, the more load the engine

will feel. According to the figure 1 below, the water

brake in the engine laboratory, at the department of

maritime studies in Warnemünde is indicated with a

green colour. The manufacturer of the water brake is

Zöllner type 9N38/12F. It has maximum power of 1200

kW and maximum speed of 3500 r/min. The required

ofwater capacity of this water brake is 25.2 . The

water temperature of water brake system should be

maintained around 40 .


(pISSN: 2541-5972, eISSN: 2548-1479) 274

Figure. 1. Engine Type MAN 6L23/30 A and Water Brake Type Zöllner 9N38/12F

B. Fuel Oil Consumption Analysis

Fuel oil consumption calculation is required to find out

the fuel gas tank volume. There are 4 parameters to

calculate the fuel oil consumption, as it can be seen in

formula 3.1 below. Main engine is not working in 24

hours per day. It is only working in 8 hours per day and

the volume of fuel gas tank will be calculated for

demand 5 days. Before calculate the fuel gas

consumption, it’s necessary to calculate the fuel oil

consumption. In this study, fuel oil consumption will be

calculated at variation loads by using formula 1 below.

(1)

In this research, there is a differences between value of

Specific Fuel Oil Consumption (SFOC) that attached in

project guide MAN 6L23/30A and data actual from

engine operation. In data retrieval, engine will be

operated in variation loads as table 1 below. By using

formula 1 and table 1 above, the result calculation of fuel

oil consumption can be seen in table 2 below.

TABLE 1.

SPECIFIC FUEL OIL CONSUMPTION

Loads

(%)

Power

(kW) RPM

SFOC from Project Guide

(g/kWh)

SFOC from Data Actual

(g/kWh)

12 115 490 229 246.96

25 240 570 217 228.33

50 480 714 197 218.13

75 720 820 193 207.78

100 960 903 194 209.06

TABLE 2.

RESULT OF FUEL OIL CONSUMPTION CALCULATION

Loads

(%)

Fuel Oil Consumption

Based on Project Guide (ton) Based on Data Actual (ton)

12 0.18 0.19

25 0.42 0.44

50 0.76 0.84

75 1.11 1.20

100 1.49 1.60

A. LNG Consumption Analysis

The calculation of LNG consumption is required to

determine the capacity of storage tank. This calculation

is using formula as shown in formula 1. When the diesel

engine is converted to dual fuel engine, the engine power

will decrease due to the differences of lower heating

value (LHV) between fuel oil and LNG. LHV is the

amount of heat released when a specified amount of fuel

(usually a unit of mass) at room temperature is

completely burned. The power decreasing and the value

of specific fuel gas consumption (SFGC) for engine

MAN 6L23/30 A will be obtained and analyzed based on

the dual fuel engine project guide, such as MAN 51/60

DF, MAN 35/44 DF, and Wartsila 34 DF.

Power Reduction of Engine MAN 6L23/30 A

In this research, the amount of power reduction of MAN

23/30 A is referenced by the engine which has been

converted to dual-fuel engines. Engine that will serve as

the reference for calculating the power reduction is MAN

48/60 B converted to MAN 51/60 DF, MAN 32/44 CR

converted to 35/44 DF, and Wartsila 32 converted to

Wartsila 34 DF (see table 3 below). To find out the

amount of power reduction of MAN 6L23/30 A, it

should be calculate the power per cylinder volume.

Therefore, power per cylinder volume of each engine can

be seen in the figure 2 below. Based on the results from

figure 2 below, thus the magnitude of power reduction

per cylinder/swept volume of each engine can be seen in

the table 4 below.


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TABLE 3.

SPECIFICATIONS OF MAN 48/60 B, MAN 51/60 DF, MAN 32/44 CR, MAN 35/44 DF, WARTSILA 32, AND WARTSILA 34 DF

No Parameter

Engine Type

MAN

48/60 B

MAN

51/60 DF

MAN

32/44 CR

MAN

35/44 DF

Wartsila

32

Wartsila

34 DF

1 Power (kW) 6900 6300 3600 3060 3480 3000

2 RPM 500 500 720 720 750 750

3 Cylinder 6 6 6 6 6 6

4 Bore (mm) 480 510 320 350 320 340

5 Stroke (mm) 600 600 440 440 400 400

6 Cylinder Volume (l) 108.6 122.5 35.4 42.3 32.2 36.3

MAN 48/60 B

MAN 51/60 DF

MAN 32/44 CR

MAN 35/44 DF

Wartsila 32

Wartsila 34 DF

10.59 8.57 16.95 12.06 18.01 13.770.00

5.00

10.00

15.00

20.00

1 2 3 4 5 6

po

we

r/cy

lind

er

volu

me

(kw

/lit

re)

engine type

Comparison Power/Litre

Figure. 2. Result of Power per Cylinder Volume Calculation

TABLE 4.

POWER REDUCTION OF ENGINE CONVERTED TO DUAL FUEL ENGINE No Engine Converted Power Reduction

1 MAN 48/60 B to MAN 51/60 DF 19.056%

2 MAN 32/44 CR to MAN 35/44 DF 28.87%

3 Wartsila 32 to Wartsila 34 DF 23.53%

To determine the value of power per cylinder volume of

engine MAN 6L23/30 A, it should be consider the result

of power per cylinder analysis of engine MAN 51/60 DF,

MAN 35/44 DF and Wartsila 34 DF. According to figure

2 above, the power per cylinder reduction between MAN

35/44 DF and Wartsila 34 DF doesn’t have differences

significantly. Comparison power per cylinder of MAN

35/44 DF and MAN 51/60 DF have differences

significantly. MAN 35/44 DF have less power, less

swept volume, and have a higher RPM compared to

MAN 51/60 DF. According to the table 4 above, the

power per cylinder reduction of MAN 35/44 DF is

higher compared to MAN 51/60 DF, it’s means when the

power is decrease, the cylinder volume is decrease but

the RPM is increase, then the reduction of power per

cylinder will increase. Therefore, the power per cylinder

reduction of MAN 35/44 DF will be used to calculate the

power reduction of engine MAN 51/60 DF. Before

calculate the power reduction, it require to calculate the

power per cylinder volume of engine MAN 6L23/30 A.

The data required to calculate the power per cylinder

volume are

Power : 960 kW

Cylinder : 6

Bore : 225 mm

Stroke : 300 mm

Based on the data above, the power per cylinder volume

can be obtained as calculation below

Swept Volume =

=

= 0.01193

= 11.93 litre

Power per Cylinder =

=

= 160 kW

Power per Cylinder Volume =

=

= 13.41

Thus, the power per swept volume in the engine

modified to dual fuel engine be


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= 13.41

= 9.54

According to the project guide of dual fuel engines that

already serve as the reference for calculating the power

per cylinder, bore dimension is having changes of 30

mm. Therefore, in this research, the bore dimensions of

the engine being 255 mm. Based on these value, swept

volume after engine modified to dual fuel engine will be

Swept Volume =

=

= 0.01532

= 15.32 litre

Engine power =

= 9.54

= 877 kW

Table 5 below shows the engine power in variation loads

after the engine modified to dual fuel engine

TABLE 5.

RESULT OF POWER REDUCTION OF ENGINE MAN 6L23/30 A AT VARIATION LOAD

Load (%) Power (kW) SFOC (g/kWh) SFOC (kJ/kWh)

100 877 208.62 8908.074

75 657.75 210.47 8987.069

50 438.50 219.90 9389.73

25 219.25 231.48 9884.196

12 105.24 250.11 10679.697

Specific Fuel Gas Consumption Analysis

The value of SFOC above is based on the data actual of

the engine operation. To determine the LNG

consumption, it’s requires the specific fuel gas

consumption data for natural gas. In this research, the

specific fuel gas consumption data of natural gas for

6L23 MAN/30 is obtained from comparative analysis of

specific fuel gas consumption of engines that already

converted to dual fuel engines such as MAN 51/60 DF,

MAN 35/44 DF, and Wartsila 34 DF. Table 6 below

shows the results of a comparative analysis of the

specific fuel consumption of those engines

TABLE 6.

COMPERATIVE ANALYSIS OF SPECIFIC FUEL GAS CONSUMPTION

Load (%)

MAN 51/60 DF MAN 35/44 DF Wartsila 34 DF

Fuel Oil

(kJ/kWh)

Fuel Gas

(kJ/kWh)

Fuel Oil

(kJ/kWh)

Fuel Gas

(kJ/kWh)

Fuel Oil

(kJ/kWh)

Fuel Gas

(kJ/kWh)

100 7643 7470 7665 7190 8113 7470

85 - - 7558 7200 7984.9 7620

75 8113 7810 7814 7330 7984.9 7850

50 8412 8390 7900 7820 8326.5 8600

25 9309 11230 8540 9000 - -

10 13237 18420 - - - -

From the table 6 above, it can be known, at load 50% -

100% specific fuel gas consumption is smaller compared

to the specific fuel oil consumption. While at load 10%

and 25%, specific fuel gas consumption is greater than

specific fuel oil consumption. Percentage change of

specific fuel consumption of this engines can be seen in

the table 7 below.

TABLE 7.

PERCENTAGE CHANGE OF SPECIFIC FUEL GAS CONSUMPTION

Load

(%)

Percentage

MAN 51/60 DF MAN 35/44 DF Wartsila 34 DF

100 -2.26 -6.20 -7.93

85 - -4.74 -4.57

75 -3.73 -6.15 -1.69

50 -0.26 -1.01 3.28

25 20.64 5.39 -

10 39.16 - -

Data in table 7 above is used as reference to determine

the value of specific fuel gas consumption of engine

MAN 6L23/30 A. With some of considerations, the

average of specific fuel gas consumption (SFGC) of

engine MAN 35/44 DF and Wartsila 34 DF will be used

to determine the specific fuel gas consumption of engine

MAN 6L23/30 A. This engine having speed of 720 RPM

and 750 RPM, where this speed is approaching to the

speed of engine MAN 6L23/30 A, while the engine

speed of MAN 51/60 DF is 500 RPM. Therefore, the

result of SFGC of engine MAN 6L23/30 A can be seen

in table 8 below


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TABLE 8.

RESULT OF TOTAL FUEL GAS CONSUMPTION ANALYSIS OF ENGINE MAN 6L23/30 A

Load (%) Average

Value (%)

MAN 6L23/30 A

Fuel Oil

(kJ/kWh)

Fuel Gas

(kJ/kWh)

100 -7.065 8908.074 8279

75 -3.92 8987.069 8635

50 2.145 9389.73 9591

The result of specific fuel gas consumption in the table 8

above is the total of specific fuel gas consumption

(Natural gas consumption + Pilot fuel consumption).

Based on MAN B&W project guide, Wartsila project

guide and DNV GL, the amount of pilot fuel oil is below

1% of the energy used by the engine. Therefore, the

amount of specific fuel consumption of pilot injector and

natural gas consumption can be seen in table 9 below

TABLE 9.

SPECIFIC FUEL CONSUMPTION OF PILOT INJECTOR

Load (%)

MAN 6L23/30 A

Total Fuel Gas

(kJ/kWh)

Pilot Fuel

(kJ/kWh)

Natural Gas

(kJ/kWh)

100 8279 82.79 8196.21

75 8635 86.35 8548.65

50 9591 95.91 9495.09

After the specific fuel gas consumption is obtained, the

fuel gas consumption at variation loads can be calculated

by using formula 1 above. Therefore, the result of fuel

gas consumption can be seen in table 10 below.

TABLE 10. RESULT OF FUEL GAS CONSUMPTION ANALYSIS OF ENGINE MAN 6L23/30 A

Load (%) Power (kW) Natural Gas (kJ/kWh) LNG Consumption

Kg/day Ton/day

100 877 8196.21 1161.71 1.16171

75 657.75 8548.65 908.75 0.90875

50 438.50 9495.09 672.90 0.6729

B. Component Selection of Fuel Gas Supply System

To supply gas from storage tank to the engine, it required

some components below.

1. LNG Storage Tank

Tank selection is based on the calculation of fuel

consumption per day. In this research, the capacity of

LNG tank that will be designed is for endurance of one

week (5 days), which means LNG tank should be able to

serve the demands of fuel engine for one week (40 hours

of engine operation). The type of the tank that will be

selected is container tank because it has advantages as

described above and also has a tank capacity of small-

sized, therefore in this study allows to choose a type of

tank container. The selected tank is horizontal cryogenic

tank type LC16H22-P with capacity 15.7 m³. It mean this

type of tank is able to serve the demand of engine

operation for a week. According to the calculation result,

the demand of LNG for a week is 12.908 m³. The LNG

fuel tank container is fitted with process equipment,

namely the valves and instruments required for

operational and safety purposes. The LNG fuel tank

container is also fitted with a pressure build-up

evaporator (PBE) for building up and maintaining an

operational pressure of approximately 5 bar in the tank.

2. Water Spray Pump

Water spray pump should be installed for supplying

water to water spray system. This system is for cooling

and fire prevention of storage tank. According to GL VI-

3-1, Section 3, 3.3.2.2, the system should be designed to

cover all areas with an application rate of 10 l/min/

for horizontal projected surfaces and 4 l/min/ for

vertical surfaces. In this research, the application rate

that will be used is 10 l/min/ because the type of the

tank is horizontal tank. Therefore, the water spray pump

capacity and the diameter pipe of water spray system can

be seen in the following calculation.

C = 10 l/min/ (2)

Where

= Surface Area of LNG tank ( )

= 63.31

C = 10 l/min/ 63.31

= 633.1 litre/min

= 37.986 /h

= 0.01056 /s

The selected water spray pump is evergush with having

capacity of 38 /h.

The following formula can be used for determining the

diameter of the pipe.

C = A v (3)

Where

C = Capacity /h

A = The area of the pipe ( )

v = Velocity, 1 m/s (Assumed)

So,

A =


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=

= 0.01056

A =

d =

=

= 0.116 m

= 116 mm

After the calculation of pipe diameter is done, it's used to

find the specification on DIN catalogue. Therefore, the

selected types of galvanised carbon steel pipe based on

DIN standard is

Inside diameter : 133.1 mm

Wall thickness : 5.4 mm

Outside diameter : 138.5 mm

Nominal diameter: DN 125

3. Vaporizer

In changing the LNG phase from liquid to gas,

vaporizer equipment is required. Vaporizer is a heat

exchange medium from liquid to gas where the heat

source can be produced from the engine fresh water

cooling, exhaust gas, and electric systems. Circulating

water vaporizer will be applied to the fuel gas system

because it’s more profitable compared to steam vaporizer

and electric vaporizer. Circulating water vaporizer has a

lower cost operation and only need hot water as a source

to vaporize LNG. Based on calculation results, the

required gas flow rate in 100% load is 145.214 kg/h. The

selected vaporizer having gas flow rate of 400 kg/h.

4. LNG Pump

LNG pump is required to transfer LNG from storage

tank to vaporizer. The LNG pump should be able operate

in maximum pressure of LNG and can operate in low

temperature, where the temperature of LNG is -182 .

The capacity of LNG pump is determined by engine fuel

gas requirement. Based on the calculation of LNG

consumption, the LNG flow rate at maximum load is

0.323 or 5.383 l/min. Therefore, the selected LNG

pump having range capacity from 1.4 – 8.1 l/min.

5. Gas Valve Unit

Before the gas is supplied to the engine, it passes

through a Gas Valve Unit (GVU). The main functions of

the Gas Valve Unit are to regulate the gas feeding

pressure to the engine, and to ensure a fast and reliable

shut down of the gas supply. Wartsila provides two

different types of gas valve unit. One is the gas valve

unit open design (GVU-OD, see figure 4) which requires

installation in an explosion-proof gas valve unit room

and airlock is required between GVU room and

surrounding space. The other is gas valve unit enclosed

design (GVU-ED, see figure 3). The gas valve unit

enclosed design is a solution where all the equipment is

mounted inside a gas tight casing. The GVU with gas

tight casing enables the installation of the gas control

system directly next to the engine in the engine room

(safe area). In this case, the cover acts as the double wall

and thus provides for a secure enclosure of the gas

control system. This will safely prevent the gas from

getting into the safe area in the event of a gas leak in the

gas control system. This arrangement allows the GVU-

ED to be placed inside the engine room to minimize

installation costs. [4].

Figure 4.9 Gas Valve Unit Enclosed Design

Figure. 3. Gas Valve Unit Enclosed Design

Figure. 4. Gas Valve Unit Open Design

Because of some considerations, in this research, GVU

open design will be installed because the engine room in

the laboratory doesn’t has enough space to install GVU

enclosed design. The selected GVU is referenced from


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Wartsila 50 DF product guide, where it’s provides two

kinds of gas valve unit enclosed design, as shown in

table 11 below.

TABLE 11.

TYPES OF GAS VALVE UNIT OPEN DESIGN

Pipe Connection GVU DN80 GVU DN100

Gas Inlet DN80 / DN125 DN100 / DN150

Gas Outlet DN80 / DN125 DN100 / DN150

In this research, the selected GVU is GVU DN 100

because the result of pipe diameter calculation of fuel

gas system is 151.4 mm or DN150.

E. Design Arrangement

1. Gas Supply System

Gas fuel supply system is a system which designed to

fulfil engine required when engine operated in variation

load. In this research, the demand of fuel gas in variation

load has been calculated.

Process of gas supply system is started from LNG

storage tank where natural gas is in liquid phase. LNG

will be transported to vaporizer by using low pressure

pump. The capacity of LNG pump is based on gas

engine required per hour. Vaporizer type that will

installed in this research is the result of comparison

between circulating water vaporizer, steam vaporizer and

electric vaporizer. In the outlet of vaporizer, natural gas

have phase changed from liquid into gas phase.

Before gas flowing to engine, previously gas will

through gas valve unit (GVU) where GVU will regulate

the pressure and temperature of gas. In every connection

in the open spaces will use a double pipe flowline.

Figure. 5. Design Arrangement of Fuel Gas Supply System

2. LNG Tank

In this research, the LNG tank that will be installed is

independent tank type C that having maximum working

pressure of 5 bar. Based on GL rules, LNG tank can be

located in enclosed deck and open deck. It’s not possible

to install the LNG tank inside the laboratory or engine

room because the laboratory or engine room, at the

department of maritime studies in Warnemünde, doesn’t

have enough space. Therefore, the LNG tank will be

installed in the open deck or outside the laboratory.

Figure 6 below shows the design arrangement and safety

aspects for LNG tank that based on Germanischer Lloyd

regulation and LNG tank manufacturer.

Figure. 6. Design Arrangement of LNG Tank

Filling Connection Every fuel gas system should be equipped with fill

connection. The function of fill connection is to provide


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a connecting point to the re-fuelling station of LNG tank.

Filling connection system also should be fitted with

liquid phase non return valve. Its function is to prevent

backflow through the fill line.

Venting System

According to GL VI-3-1, Section 2, 2.8.1.3, pressure

relief valve should be fitted to the LNG tank. Single

pressure relief valve will be installed because the tank

volume not exceeding 20 . According to GL I-1-6,

Section 8, 8.2.1, when the volume cargo tank exceeding

20 is to be fitted at least two pressure relief valve.The

pressure relief valve is set at the maximum allowable

working pressure (MAWP) of the tank. Based on GL VI-

3-1, Section 2, 2.8.4.1, gas in liquid state may be stored

with a maximum allowable working pressure of 10 bar.

Therefore, its function is to vent product to atmosphere if

the tank pressure exceeding of 10 bar. In the venting

system also equipped with line safety valve. Its function

is to vent produce to atmosphere in the event of a

malfunction of the pressure relief valve.

Pressure and Level Indicator for LNG Tank

According to GL VI-3-1, Section 5, 5.2.1 and 5.2.2,

storage tank should be monitored with overfilling and

pressure indicator. Where, storage tanks for liquid gas

should not be filled to more than 95% of tank capacity

and the maximum working pressure of 10 bar inside the

storage tank. This number is based to the GL rules and

LNG tank manufacturer. Therefore, a liquid level and

pressure indicator should be fitted to prevent the LNG

tank from becoming liquid full and over pressure.

Pressure Build-up Unit

In the pressure build-up process, cold LNG is drained

from the tank bottom to the PBU. The flow is controlled

by valve which located before the PBU on figure 5.2

above. According to the LNG tank manufacturer, the

operation pressure is set 5 bar. When the pressure drops

below 4.5 bar, the PBU is activated and it is de-activated

when the tank pressure increases above 5 bar. PBU cycle

is driven by the thermosyphon effect: the flow through

the PBU is not driven mechanically by a pump or

similar, but by the heat transferred into the circuit in the

PBU. The difference in density between LNG and NG

gives a difference in the static pressure between the

section from the liquid surface in the tank to the bottom

of the PBU and the section from the bottom of the PBU

through the PBU and back to the liquid surface. This

enables the fluid to flow around in the circuit [5]. PBU

converts liquid from the tank into gas and returns it to

the tank, as a result of which the pressure in the tank can

be increased.

3. Water Spray System

According to GL VI-3-1, Section 3, 3.3.2.1 and

3.3.2.2, when the storage tank located on open deck, a

water spray system should be fitted for cooling and fire

prevention. The system should arranged to cover all

areas with an application rate of 10 l/min/ for

horizontal projected surfaces and 4 l/min/ for vertical

surfaces.

The capacity of the water spray pump should be

sufficient to deliver the required amount of water as

specified in GL VI-3-1, Section 3, 3.3.2.2. The capacity

of water spray pump can be seen in chapter 4.2. The

system shall be initiated automatically by the fire

detection system. On detection of fire on any one storage

tank, the water spray system on an adjacent storage tank

shall operate by opening the control valve (spray valve).

Construction materials can be chosen by the client, based

on the possible corrosive properties of the environment

or of the used water. Control valves can be made of cast

steel as well as from bronze, alubronze, stainless steel or

duplex steel. Spray nozzles can be made of bronze or

stainless steel. Piping shall be made of galvanized carbon

steel [6].

4. Ventilation in double piping system

According to GL VI-3-1, Section 2, 2.7.1.1, gas

piping system should be arranged with double wall

piping. The space between the gas fuel piping and the

wall of the outer pipe or duct should be equipped with

mechanical under pressure ventilation. Ventilation air

inlet is located at the engine and the outside of the tank

connection space at the end of the double wall piping.

Ventilation air is recommended to be taken from the

outside of the engine room and safe area and equipped

with a valve to regulate the air flow. The requirement of

air exchange in double piping system is minimum 30 air

changes per hour, these number is based of classification

societies of Germanischer Lloyd. Air flowing will be

supplied to Gas Valve Unit room or to the enclosure of

the gas valve unit. From the enclosure of the gas valve

unit, the air will be ventilated by using ventilation fans

and the air will be supplied to the safe area. According to

GL rules, the ventilated air outlet should be placed in a

position where no flammable gas and air mixture may be

ignited and should be installed the gas detector to control

any losses of the required ventilating capacity.

5. Gas Valve Unit

In gas valve unit (GVU) system, there are 6 pipes

connections, such as: gas inlet connection, gas to engine

connection, inert gas connection, gas venting connection,

air venting connection, and instrument air connection.

Gas is flowing to GVU system through gas inlet

connection where the gas pressure is 5 – 10 bar(g). Gas

will be filtered by a filter with maximum mesh width

must be 0.005 mm [7]. The pressure loss at the filter is

monitored by a differential pressure gauge. Before

entering the engine, the gas pressure will be measured by

pressure gauge, and gas also through double block and

bleed valves.


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Figure. 7. Design Arrangement of Gas Valve Unit

According to GL GL VI-3-1, Section 5, 5.6.3, fuel gas

supply system should be provided with double block and

bleed valves. Block valve will open when there is no

failure occurred in the system. In the event of a failure in

the gas supply system then the block valve will be closed

and venting valve or bleed valve will automatically open.

The function of the vent valve is to reduce the pressure

of the gas in the pipeline and the gas can be ventilated

outside the atmosphere. Connecting the engine or

venting lines to the GVU LNGPac venting mast is not

allowed, due to risk for backflow of gas into the engine

room when LNGPac gas is vented. In gas valve unit

system, there is a gas double wall system ventilation fan

connection for supplying the air inside the GVU room to

the safe area. According to GL rules, the maximum of

ventilation fan capacity is 30 times per hour and the

maximum length of the fuel gas pipe between GVU and

gas inlet at engine should be kept as short as possible and

not exceed 30 m.

6. Inert gas system

In gas valve unit system, there is a gas inert

connection where before maintenance work is

commenced on the engine and/or the GVU, it is required

that any remaining natural gas is removed by substituting

the natural gas

with an inert gas, for example nitrogen. The GVU

inerting process ensures that natural gas cannot leak to

the surrounding areas, thus eliminating potential risks. If

there is a failure of fuel gas supply system, block valve

will be automatically closed and vent valve will be

automatically opened. During this situation, the piping

will be automatically purged with inert gas system,

therefore on the dual fuel engine, an inert gas valve

should be installed. In case the nitrogen purging system

fails, the gas pipe is once purged with charge air and a

gas blocking is set. Thus an explosive atmosphere can

only occur seldom and for short periods. Operation in

gas mode is only possible if Nitrogen pressure is

available and gas blocking alarm has been reset by

operator.

IV. CONCLUSIONS

Based on the calculation result and design process of

concept fuel gas supply system for laboratory, at the

department of maritime studies in Warnemünde, there

are some conclusions can be obtained as below:

1. The LNG and fuel gas consumption calculation of

engine MAN 6L23/30 A is as table 12 below

TABLE 12.

LNG AND FUEL GAS CONSUMPTION PER DAY

MAN 6L23/30 A

Loads LNG Consumption

( /day)

Natural Gas Consumption

( /day)

100% 2.58 1548

75% 2.02 1212

50% 1.50 900

Natural gas consumption is required to determine the

specification of vaporizer, pipe diameter, and gas valve

unit specification. According to natural gas facts (2004),

the original volume of the LNG being converted into

natural gas by a factor 600. LNG consumption

calculation result is required to determine the capacity of

LNG tank. In this LNG tank arrangement, the LNG tank

should be able to serve the engine operation during one

week (5 days). Based on the calculation result, the total

LNG consumption per week is 12.908 .

2. The selected components of fuel gas supply system

can be seen in table 13 below


(pISSN: 2541-5972, eISSN: 2548-1479) 282 TABLE 13.

THE SELECTED COMPONENTS OF FUEL GAS SUPPLY SYSTEM

Object Value Measurement Unit

LNG Tank

Series 2200 H Model LC16H22-P

Volume 15.7 Stored Liquid

Weight at 95% 6.9 Ton

Water Spray Pump

Manufacturer Evergush

Type XA50/26

Q 38 Head 19.8 m Speed 1450 RPM

Required Motor 4 kW

Vaporizer

Vaporizer Type Circulating Water Model VWB-400

LNG Flow Rate 400 kg/h

Water Flow Rate 5.1 LNG Pump

Manufacturer Vanzetti Type VT-1 32 25

Q 1.4 – 8.1 lpm

Power Installed 3 - 15 kW

Gas Valve Unit

Manufacturer Wartsila

Type GVU DN 100

3. In this concept design of fuel gas supply system,

there are three types of piping system that should be

installed, such as pipe for liquid phase from LNG

tank until the input of vaporizer, pipe for gas phase

from output of vaporizer until engine manifold and

pipe for water spray system. All the dimensions are

accordance to DIN standard. The dimension of this

pipe can be seen in table 14 below

TABLE 14.

PIPE DIAMETER DIMENSION

Object Value Measurement Unit

Pipe Dimension of Gas Phase

Inside Diameter 152.4 mm

Insulation Thickness

50 mm

Annular Gap 21 mm

Outside Diameter 304.8 mm

Pipe Dimension of Liquid Phase


Insulation Thickness

20 mm

Annular Gap 17 mm


Pipe Dimension of Water Spray System


Wall Thickness 5.4 mm


Nominal Diameter

DN 125

4. The location of each components should be

considered based on the regulation to achieve the

optimum design arrangement. According to GL rules,

LNG tank can be located in the opened space and

closed space. In this design arrangement, the LNG

tank located in the open space because the laboratory

doesn’t have enough space. The gas valve unit is

enclosed design type because it can be located inside

the engine room and it’s not require installation in an

explosion-proof gas valve unit room. All the

equipment of gas valve unit type enclosed design is

mounted inside a gas tight casing and it can minimise

the installation costs. LNG pump and vaporizer are

located in the open space to avoid a gas explosion

when operating failure occurred on LNG pump and

vaporizer.


(pISSN: 2541-5972, eISSN: 2548-1479) 283

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